Functional Patterns

Functional programming patterns: pure functions, immutability, composition.

Language / Topic

Ruby

Rules

Functional Patterns · balanced balanced

- Prefer pure functions: given the same inputs, always return the same output with no side effects.

- Use immutable data structures; avoid mutating variables or objects after creation.

- Favor function composition and pipelines over deeply nested logic.

- Use higher-order functions (map, filter, reduce) instead of manual loops for collection transformations.

- Separate side effects (I/O, network, state) from pure computation; push effects to the edges of your program.

- Prefer declarative code that describes *what* to compute rather than *how* to compute it step by step.

- Use closures and partial application to create reusable, configurable function factories.